So far, ultrahigh pressure water jetting equipment and sand blasting equipment have been put to practical use as surface treating devices which eject a high pressure fluid such as water or a high pressure fluid mixed with abrasives, toward the surface of an object such as an oil storage tank or a ship hull, thereby removing foreign matter such as an old coating or rust, stuck onto the surface of the object, or roughening the surface of the object with the abrasives ejected, to make the surface ready for coating; or a device for cleaning the surface of the object to carry out non-destructive testing.
In Japanese Patent Publication No. 26752/1985 and the specification and drawings of U.S. Pat. No. 4,095,378, there is disclosed devices which can be exemplified as a surface treating device which ejects a high pressure fluid such as water or a high pressure fluid mixed with abrasives, toward the surface of an object while suction-adhering to the surface of the object by the pressure of an ambient fluid such as air or water and moving along the surface, thereby removing foreign matter, such as an old coating or rust, stuck onto the surface of the object, or roughening the surface of the object with the abrasives ejected, to make the surface ready for coating; or a device for cleaning the surface of the object to carry out non-destructive testing.
Such a device comprises a blasting case, wheels as moving means mounted on the blasting case, a suction-adhering seal connected to the blast case and having its free end portion adapted to make contact with a surface of the object, and a pressure reduction means for discharging a fluid from a pressure reduction space defined by the blasting case, the surface of the object and the suction-adhering seal.
When the pressure reduction means is energized in this device, the fluid within the pressure reduction space is discharged outside, and the pressure of the fluid acting on the blasting case of the device owing to the difference in fluid pressure between the inside and the outside of the pressure reduction space is transmitted to the surface of the object via the wheels, and the fluid pressure causes the device to suction-adhere to the surface.
When, in this suction-adhering state, the wheels are rotated by driving means such as an electric motor, the device moves along the surface of the device by the action of the wheels.
Further, such a device is provided with a working unit of an abrasives-blasting means such as a nozzle which ejects abrasives to the surface of the object.
In conventional abrasives-blasting equipment using compressed air, a mixed fluid which is composed of about 13 m.sup.3 /min. of compressed air pressurized to about 6 kg/cm.sup.2 and about 35 kg/min. of non-steel abrasives is ejected from a nozzle with a diameter of about 15 mm, the nozzle is swung at a swing angle of from about 60 degrees to about 90 degrees to treat by abrasives about 400 mm in width on the surface of the object, and further, the swung nozzle is gradually moved in the direction which intersects at right angles with the swing direction along the surface of the object at a rate of about 1.8 m/min. Thus, the surface is treated continuously.
The conventional device described above, however, involves the following problems to be solved.
That is, in conventional abrasives air-blasting equipment using compressed air, the treated surface has unevenness in treatment that is caused by change of distance between the surface of the object and the tip of the nozzle depending on a swing angle of the nozzle. Further, it is difficult for the device to maintain a low height from the surface of the object because unevenness in treatment becomes greater when the swing angle is set to above 90 degrees for the purpose of obtaining a device with the lower height from the surface of the object.
Incidentally, a device whose height from the surface of the object is high is difficult to use in a narrow space.
Whereas, in conventional ultrahigh pressure water jetting equipment, about 20 liters/min. of water pressurized to an ultrahigh pressure of about 2,000 to about 2,500 kg/cm.sup.2 is ejected from a nozzle with a diameter of 0.1 to 0.5 mm, and a nozzle with a revolution diameter of about 400 mm is revolved at a speed of about 1,000 rpm on a plane parallel to the surface apart from the surface of the object by 20 to 30 mm, the revolving nozzle being gradually moved along the surface of the object at a speed of about 3 m/min. Thus, the surface of the object is treated continuously.
Such a device has a swivel joint for connecting the nozzle and an ultrahigh pressure water hose which supplies the ultrahigh pressure water to the nozzle.
In conventional ultrahigh pressure water jetting equipment, a mixing nozzle in which abrasives are mixed into ultrahigh pressure water on the downstream side of the nozzle is provided as a means for mixing the abrasives into an ultrahigh pressure water stream because it is difficult to mix abrasives having a larger size than the diameter of the nozzle into the ultrahigh pressure water stream prior to ejecting the abrasives from the nozzle for the reason that the diameter of the orifice of the nozzle is too small for ejecting of the abrasives.
The conventional device described above, however, has the following problems to be solved.
That is, in conventional ultrahigh pressure water jetting equipment, it is difficult to mix abrasives into an ultrahigh pressure water stream to be ejected from a revolving nozzle. The reason is because it is difficult to produce such a swivel joint having two-phase flow for supplying separately the ultrahigh pressure water and the abrasives to the revolving nozzle.
Furthermore, the conventional device described above, however, has the following problems to be solved.
That is, in a conventional ultrahigh pressure water jetting equipment, because of the difficulty in mixing abrasives into an ultrahigh pressure water stream ejected from the revolving nozzle it is difficult to remove hard rust although soft coatings are easily peeled off.
Further, an anchor pattern, i.e., roughness, can not be formed on the surface of the object in the conventional ultrahigh pressure water jetting equipment because its formation absolutely requires that abrasives must be ejected toward and impinged on the surface of the object.
A main object of the present invention to overcome the technical problems is, therefore, to provide, in abrasives air-blasting equipment using compressed air or ultrahigh pressure water jetting equipment, a surface treating device which is capable of effectively treating the surface of the object without generating unevenness in treatment by allowing a nozzle to move, in parallel, along the surface of the object without using swivel joint as means for feeding a high pressure fluid or a high pressure fluid mixed with abrasives to the nozzle and which can be used in a narrow space owing to its reduced height.
Another object of the present invention is to provide, in a surface treating device capable of being suction-adhered to the surface of an object such as an oil storage tank or ship hull owing to the pressure of the ambient fluid such as the air or water and moving therealong, a surface treating device which is capable of effectively treating the surface of the object without generating unevenness in treatment by allowing a nozzle to move, in parallel, along the surface of the object without using a swivel joint as means for feeding a high pressure fluid or a high pressure fluid mixed with abrasives to the nozzle and can be used in a narrow space owing to its reduced height, and further in which old coatings or abrasive grains peeled off from the surface of the object are prevented from scattering to the outside of the device thereby to not contaminate the environment and which is safe because it can be operated by a remote-control mode.